A tragic coil
From: mark [SMTP:moyson-at-tig-dot-com.au]
Sent: Saturday, February 21, 1998 4:30 AM
To: Tesla List
Subject: Re: A tragic coil
>> 3. I replaced the 630V caps with a bank of 3KV caps and then a strange thin
>> happened. When I turned it on....no sparks but absolutly MASSIVE RF
>> interference. The tv in another room lost the reception (I was told) and the
>> auto garage door opened up by itself and went "haywire" till I turned the
>> coil off. It also lit up a neon light at about 10cm from the coil.
>> What is going on here?????? I am totally lost now!!!!
>Your primary tank circuit must be tuned to oscillate at the same
>frequency as your secondary for optimal operation. When you changed the
>tank cap did you retune the system?
I recalculated the capacitance and inductance and tried to mach up the
values as best I could!
I am having a hell of a time tuning this coil....never before has there been
so many problems.
>If the secondary doesn't "break out" (start throwing streamers), you
>will generate large amounts of RFI, much to the consternation of your
>equipment and possibly your neighbors. Place a small sharp object (a
>nail, short piece of wire, or a thumb tack, point up, on top of the
>discharge terminal and carefully tune for maximum spark at lower power
>levels. Once you're in tune, you can then bump the power level upwards.
>>From your description, it sounds like you DO have insulated wire on your
>secondary. You want the turns to touch to maximize inductance (and the
>Q) of your secondary. Do you have a good RF ground connected to the base
>of your secondary?
Malcom said that it was a good ground!
If you have relatively few turns on the secondary,
>this may be one of the major reasons why the coil is a poor performer. A
>tight-wound secondary, with moderate gauge (#22-26 AWG) wire will give
>you better performance.
This prewound coil looks to have 30AWG wire.
>BTW, I'd also bet that the 630 volt caps you used were oil-immersed
>mylar filter caps. The dielectric heats up quite rapidly under RF
>conditions, and since they are sealed, the pressure builds up internally
>until they blow, showering you with hot oil (sometimes PCB's) and
>capacitor fragments. What kind of caps are you using now?
I am using a bank of 3KV caps....new ones Ive never seen before! They seem
to be really good but pricy at $1.95 a pop.
Also I have seen a high pulse discharge cap for strobe lights rated at 7ufd
and 250VAC. Could you use this in any way??
>Check out the archives on Chip's website or on Funet for LOTS of solid
>information on caps, coils, tuning, etc...
>Safe, unexplosive, coilin' to you!
>-- Bert --
Thank you Bert!